Develop Reference

FlaskSocket-IO configuration with Nginx and Gunicorn

Not sure if I misconfigured my application but I am getting the following error from my FlaskSocket-IO application in /var/log/nginx/error.log. Could someone advice what went wrong?
2022/11/17 17:23:48 [crit] 132962#132962: *330 connect() to unix:/home/ubuntu/python_flask/python_flask.sock failed (2: No such file or directory) while connecting to upstream, client: 70.51.xxx.xxx, server: www.somesite.io, request: "GET /socket.io/?EIO=3&transport=websocket HTTP/1.1", upstream: "http://unix:/home/ubuntu/python_flask/python_flask.sock:/socket.io/?EIO=3&transport=websocket", host: "www.somesite.io"
Below you can also see how I have configured NginX and Gunicorn service.
/etc/nginx/sites-enabled/somesite.io
server {
listen 80;
server_name www.somesite.io somesite.io;
access_log /var/log/nginx/example.log;
location /socket.io {
proxy_pass http://unix:/home/ubuntu/python_flask/python_flask.sock;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";
}
location / {
proxy_pass http://unix:/home/ubuntu/python_flask/python_flask.sock;
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
}
server {
listen 443 ssl;
listen [::]:443 ssl;
server_name www.somesite.io somesite.io;
location /socket.io {
proxy_pass http://unix:/home/ubuntu/python_flask/python_flask.sock;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";
}
location / {
proxy_pass http://unix:/home/ubuntu/python_flask/python_flask.sock;
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
ssl_certificate /etc/letsencrypt/live/somesite.io/fullchain.pem;
ssl_certificate_key /etc/letsencrypt/live/somesite.io/privkey.pem;
}
/etc/systemd/system/gunicorn3.service
[Unit]
Description=Gunicorn Service
After=network.target
[Service]
User=ubuntu
Group=www-data
WorkingDirectory=/home/ubuntu/python_flask
ExecStart=/usr/bin/gunicorn3 --workers 1 --bind unix:python_flask.sock -m 007 app:app

Flask app running with gunicorn and nginx is crashing at redirecting point

Can you please help? I am stuck.
My server is crashing at #return redirect(url_for(‘login’)) ,when I run it using gunicorn i.e. $gunicorn — bind 127.0.0.1:5000 -w 4 wsgi:app.
Same issue arises when I run it using supervisor.
The code is working fine when I run it normally i.e. python app.py
Appreciate any suggestions.

Try using this config, might help you.
Create a new file in /etc/nginx/sites-enabled/
server {
listen 80 ;
server_name abc.com;
large_client_header_buffers 8 32k;
if ($http_user_agent ~* Googlebot) {
return 403;
}
access_log /var/log/nginx/access.log;
location / {
add_header 'Access-Control-Allow-Origin' "$http_origin";
add_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, DELETE, PUT';
add_header 'Access-Control-Allow-Credentials' 'true';
add_header 'Access-Control-Allow-Headers' 'User-Agent,Keep-Alive,Content-Type';
proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_pass https://127.0.0.1:5000;
proxy_read_timeout 90;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
proxy_buffers 8 32k;
proxy_buffer_size 64k;
}
}
use
nginx -t reload
check the config

Flask with gunicorn on nginx 502 bad gateway error

After some ubuntu 16.04 upgrades and app code modifications, my Flask on gunicorn and nginx website which previously was working is now giving a 502 bad gateway error.
myapp.conf:
upstream app_server_wsgiapp {
server localhost:8000 fail_timeout=0;
}
server {
listen 80;
server_name www.myserver.com;
access_log /var/log/nginx/www.myapp.access.log;
error_log /var/log/nginx/www.myapp.error.log info;
keepalive_timeout 5;
location /static {
autoindex on;
alias /myapp/static;
}
location / {
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_redirect off;
if (!-f $request_filename) {
proxy_pass http://app_server_wsgiapp;
break;
}
client_max_body_size 2097152;
#to get around upstream sent too big header while reading response header from upstream error
proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
}
# this section allows Nginx to reverse proxy for websockets
location /socket.io {
proxy_pass http://app_server_wsgiapp/socket.io;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";
}
}
/var/log/nginx/myapp.error.log
2017/06/11 06:42:52 [error] 31054#31054: *1 connect() failed (111: Connection refused) while connecting to upstream, client: clientip, server: www.myserver.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8000/", host: "www.myapp.com"
From my apps log file I note that Flask gets part of the way through starting up, then restarts in a continuous fail/restart loop.
Any ideas how I can go about debugging what could be causing this issue?

Looks like the problem is caused by flask app running error. Could you please try to run the app in interactive way? With same params and environment settings in daemon way and check whether the service can be started correctly?

https not workking AWS ELB(ssl cert) + FLASK + NGNIX

I have a AWS Load balancer with SSL which is pointing to a ec2(windows) on 80, i.e on LB,
https 443 http 80
However the app i'm running is on another port 9100 which is configured in ngnix, now i'm unable to access the server via https
Please help me out on this
here is my nginx config,
server {
listen 80;
server_name mydomain.com;
location / {
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto https;
proxy_pass http://127.0.0.1:9100;
proxy_connect_timeout 150;
proxy_send_timeout 100;
proxy_read_timeout 100;
proxy_buffers 4 32k;
client_max_body_size 8m;
client_body_buffer_size 128k;
}
}

There are many examples of Nginx with https around. Merging the Nginx HTTPS documentation with your sample configuration gives something like:
server {
listen 80;
listen 443 ssl;
server_name mydomain.com;
ssl_certificate www.example.com.crt;
ssl_certificate_key www.example.com.key;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
location / {
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto https;
proxy_pass http://127.0.0.1:9100;
proxy_connect_timeout 150;
proxy_send_timeout 100;
proxy_read_timeout 100;
proxy_buffers 4 32k;
client_max_body_size 8m;
client_body_buffer_size 128k;
}
}
This will get Nginx to serve traffic as HTTPS on port 443. You would need to update the ELB to send HTTPS traffic to port 443 if it's coming via that device.
You would also need to update the Nginx ssl_certificate & ssl_certificate_key options to point to somewhere on the EC2 instance that contains those files.

Socket-Management in Nginx with Flask - Why is Cross-Origin Request Blocked?

I want to create a socket in Flask-SocketIO through Nginx and Unicorn. The following configuration works on localhost without Nginx.
When I access the web application through Nginx in Chrome, i get the error:
Failed to load resource: Could not connect to the server.
http://52.34.18.48:6419/socket.io/?EIO=3&transport=polling&t=1454455363683-6
When I access the web application through Nginx in Firefox, I get the error:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading
the remote resource at
http://52.34.18.48:6419/socket.io/?EIO=3&transport=polling&t=1454464333740-25. (Reason: CORS request failed).
This is how I initialize the socket connection in JavaScript:
import io from "socket.io-client"
const socketUrl = 'http://' + document.domain + ':6419' + '/FlaskApp'
const socket = io(socketUrl);
export default socket;
My Nginx config file looks like this:
server {
listen 80;
server_name 52.34.18.48;
error_log /var/www/Flaskapp/nginx_errorlog.log;
access_log /var/www/Flaskapp/nginx_accesslog.log;
root /var/www/Flaskapp;
location /socket.io {
proxy_pass http://127.0.0.1:6419/socket.io;
proxy_redirect off;
proxy_buffering off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
location / {
proxy_pass http://127.0.0.1:6419;
proxy_buffering off;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_set_header Host $host;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";
}
The Gunicorn command I used is:
gunicorn --worker-class eventlet -w 1 -b 127.0.0.1:6419 flask_app:application
I wrapped the socket in the Flask application like this.
from flask_app import application
from flask_socketio import SocketIO
socketio = SocketIO(application)
Why do I get this error via Nginx but not when connecting via localhost? How can I access the socket.io via Nginx correctly?